How to check `toHaveBeenCalledWith` with same function

Question

I was trying to check the return value its passed but when i expect toHaveBeenCalledWith same function it gets failed with no.of calls is:0. Can anyone tell me whats wrong in this code?

 describe('buildAggregateParams', () => {
    // Preparing
    const schemaParams = {
      filterKeyMap: {
        id: '_id',
        name: 'test_name',
        no: '_no',
      },
      sortKeyMap: {
        date: '_created_date',
        no: '_no',
        name: 'test_name',
        status: '_status_is_active',
      },
      lookups: [
        {
          from: 'sample',
          localField: 'test_id',
          foreignField: '_id',
          as: 'test_id',
          model: 'sampleModel',
        },
      ],
      unwinds: [],
      queryKeys: ['page', 'size', 'sort', 'order_by', 'from', 'to', 'status'],
    };
    const entityName = 'test_collection';



    it('test 1.', async () => {
      // Preparing
      const request = ({
        query: {
          price_fromss: '2',
        },
        originalUrl: '/api/m3/product/all/?price_fromss=2',
      } as unknown) as Request;
      const expectBuildAggregateParamsResult = {
        filters: { test_collection_status_is_active: true },
        pageSort: { limit: 25, skip: 0, sort: {} },
        filterKeyMap: { id: '_id', name: 'test_name', no: '_no' },
        sortKeyMap: {
          date: '_created_date',
          no: '_no',
          name: 'test_name',
          status: '_status_is_active',
        },
        lookups: [
          {
            from: 'sample',
            localField: 'test_id',
            foreignField: '_id',
            as: 'test_id',
            model: 'sampleModel',
          },
        ],
        unwinds: [],
        queryKeys: ['page', 'size', 'sort', 'order_by', 'from', 'to', 'status'],
      };

      const ff = jest.spyOn(ControllerUtility, 'buildAggregateParams'); 
      // Executings
      const result = await buildAggregateParams(request as Request, schemaParams, entityName, {
        price_fromss: jest.fn(),
      });
      expect(result).toEqual(expectBuildAggregateParamsResult); // Passed
expect(ff).toHaveBeenCalledWith(request as Request, schemaParams, entityName, {
        price_fromss: jest.fn(),
      }); //Failed
    });
  });

Answer 1

price_fromss is not the same function, jest.fn() !== jest.fn(). In order to pass the equality check it should be the same:

  const price_fromss = jest.fn();
  const result = await buildAggregateParams(request as Request, schemaParams, entityName, {
    price_fromss
  });
  expect(ff).toHaveBeenCalledWith(request as Request, schemaParams, entityName, {
    price_fromss
  });

Or for a case when it's impossible to keep a reference to a function:

  expect(ff).toHaveBeenCalledWith(request as Request, schemaParams, entityName, {
    price_fromss: expect.any(Function)
  });

The assertion doesn't serve a good purpose because it tests the line you've just written and not the unit.